Reverse circulation expansible rotary drill bit with hydraulic lock

ABSTRACT

A rotary drill bit having expansible cutters shiftably supported on a main body and expansible by a mandrel upon relative longitudinal movement of the main body and the mandrel, and in which a quantity of liquid is initially confined in a chamber to prevent such relative longitudinal movement, a closure being movable to release the fluid when expansion of the cutters is desired. Such a drill bit in which an enlarged flow passage is closed and fluid passes through a smaller opening during initial circulation of drilling fluid to provide operating fluid pressure differential for expanding the cutters, the enlarged opening allowing for free flow of drilling fluid following expansion of the cutters.

United States Patent 2,049,450 8/1936 Johnson 175/267X 4 \1 i-e7- 52 213 aa 2 a5 I27 40a. 49 e2 49 "if? I a gnngi ggeggsa [72] Inventor Archer W. Kammerer, Jr. 2,699,921 1/ 1955 Garrison 175/267 Fullerton, Calif. 2,755,070 7/1956 Kammerer 175/267 [21] Appl. No. 761,947 3,137,349 6/1964 Garrett 166/196 [22] Filed Sept. 24, 1968 3,196,960 7/1965 Kammerer 175/267 Patented Jan. 12, 1971 3,339,647 9/1967 Kammerer 175/268 [73] Assignee Row-y Oil Tool Company 3,406,769 10/1968 Kammerer 175/269 Buena Pal-beam 1 Prima Examiner-Marvin A. Cham ion a of Cahfomla' by mesne Assisra iit Examiner-Ian A. Calvert p asslgnmems Atrorrrey-Bernard Kriegel w [54] ROTARY AESTRACT: A rotary drill bit having expansible cutters 19 Claims, 5 Drawing Figs. shrftably supported on a mam body and expansible by a mandrel upon relative longitudinal movement of the mam body [52] U.S.Cl. 175/268, the mandrel and in Which a quantity 0f liquid is initially l/271,175/318 confined in a chamber to prevent such relative longitudinal [51] Int. Cl. E2lb 9/26 movement, 3 Gimme being movable to release the fl id when [50] Field of Search /267- expansion of the cutters is desired s a drill bit in which an 269,271,290, 318; 166/553 196 enlarged flow passage is closed and fluid passes through a smaller 0 enin during initial circulation of drilling fluid to [56] References Cited provide ogeratiig fluid pressure differential for expanding the UNITED STATES PATENTS cutters, the enlarged opening allowing for free flow of drilling fluid following expansion of the cutters.

I rim REVERSECIRCULATION EXPANSIBLE ROTARY DRILL BIT WITII HYDRAULIC LOCK In the use of expansible drill bits having cutters pivotally mounted on a main body so as to be expanded outwardly to mill casing set in a bore hole or to underream a bore hole, cleaning of the cuttings from the hole by the flushing action of the drilling fluid is sometimes a problem. If the volume of drilling fluid in the annulus between the drill pipe and bore hole or casing is great, as compared with the volume of drilling fluid in the drill string, normal circulation procedure, namely, down the drill string and upwardly through the annulus, results in low fluid velocity in the annulus, thereby giving rise to the possibility that the cuttings may fallout of the upwardly flowing drilling fluid. However, if the flow of drilling 'fluid is reversed, the upward flow of fluid in the drill string is at a greater velocity, thereby enhancing the ability of the fluid stream'to carry the cuttings to the top of the well. This latter type of operation is known in the field as reverse circulation."

In my pending patent application filed Oct. 24, 1966, Ser. No. 588,947, for Reverse Circulation Rotary Expansible Drill Bits," now Pat. No. 3,406,769, there are disclosed reverse circulation expansible rotary drill bits adapted for passing through a well casing so as to enlarge the well bore below the casing upon expansion of the cutters, or capable of severing or milling away a section. of the. casing. The cutters of that application are. capable of expansion responsive to the reverse circulation ofdrillingfluid Running of such'bits may result in problems such as the tendency of the cuttersto beprematurel'y, expanded. The use of such bitsmay'result-in problems s'uch'as the tendency'of the orifice, through which fluid flows, to produce a pressure drop and resultant pressure differential for-initiating expansion of the cutters, to'becomeplugged or blocked by'cuttings passing upwardly through-the drillbit,

Thepresent invention providesastructure whereby'during running-of an expansible cutter-type rotary drillbit, thecutters are positivelyh'eld'in a retracted condition, so that thebit assembly easily passes downwardly through thewell casing.

More specifically, the invention. provides a chamber between the main cutter supporting-body and the cutter expandingmandrel, the chamber being adapted to contain a quantity of hydraulic fluid trapped-therein, but releasable whenit is desired to permit relative longitudinal movement between the body and the mandrelto effect expansion of the bit cutters. In accomplishingthis result, the hydraulic fluid is trapped in the cha'mber'by. a sleeve, or the like, which is latched in a first. position-t closeoneor more exhaust; ports leading from the chamber, this 'sleeve' being 'shiftable to *a second position at which it is adapted to be latched and at which position the-exhaustport or ports are openedafor comweight of the drill string is then applied to the cutters through the mandrel, whereby the cutters remain expanded for continued drilling. During continued drilling. the restricted passage is not required to produce the differential pressure for initiating expansion of the cutters, but if drilling fluid is required to flow into the drill string solely through such a restricted passage, there is a tendency for large cuttings to bridge in the restricted passage and block flow through the same.

Accordingly, the invention also provides a structure in which an enlarged flow passage is opened to allow a large flow I path for drilling fluid and cuttings upwardly through the bit asmunication with theed'rilling, fluid so that: the necessary relamove into engagement with; the sleeve bythe downwardflow of-drillingfluid in the-drillstring, the ballseating on the sleeve and enabling the "pressure of drilling fluid to actuate the sleeve to'its second'position. Thereafter, the ball will'returnto the topof'the drill string-duringreverse circulation of the drilling fluid;

In addition, the. invention provides astructurewhereby the tendency of plugging'of the bit bycuttings is reduced.

More specifically,.in one embodiment of the invention, reverse circulation .ofdrilling fluidinitiates outwardexpansion of the drilling ormilling cutters dueto the differential pressure acting on .the cutter: supporting body, caused. by the flow of drilling fluid upwardly through a restricted passage, thebody thus being moved upwardly-relative to the cutter expanding mandrel. Rotationof the drillstringduringtthe.initial'expansion of -the cutters causes the cutters to form a slioulder in the .have been initially expanded.

In accomplishing this purpose, the invention provides a mandrel portion having a port or ports of a flow area substantially equaling or greater than the area of the central flow passage through the'mandrel, which port or ports are opened upon initial opening or expansion of the cutters in response to differential pressure acting on'the cutter supporting body to move the latter relative to the mandrel. Such differential pressure may be caused by fluid flow through a smaller port while the larger port is closed.

Among the objects of the invention is the provision of a rugged expansible cutter-type rotary bit operable by reverse circulation, which is trouble-free in running and in operation, being incapable of premature expansion and not being susceptible to plugging by cuttings.

This inventionpossesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present specification. These forms will now be described in detail'for the purpose of illustrating the general principlesof the invention; butit is to-be understood thatsuch detailed description is notto be taken'in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIG. 1 is a longitudinalsectionthrough'a rotary expan'sible drill bit'disposed in awell bore, with thecutters hydraulically lockedin retracted'positions-and with the enlarged circulation passage closed;

FIG. 2 is a fragmentary longitudinal section illustrating-the release of the hydraulic lockto enable expansionof' the cutters;

' FIG. 3 is a'longitudinal section correspondirig to-FIG. I ,.but-- showing the parts of the'drill bit with the cutters fully expanded, and the enlarged circulating passage open;

FIG. 4 is a fragmentary longitudinal section showing" a:- modified structure'p'roviding an initially closedenlarged' cir'cu lationpassage, with the cutters in'retracted positions;' and FIG. 5 isa view'eorres'ponding to'FlG; 4, but'showingJthe parts of the drill bit-with= the'cutters expanded. an'd the en larged circulating passage open.

Asshown in thedrawings, arotary exp'ansible drill bi t k is" secured to' the lower end of astring of drillpipe B were; extending to-the top of a borehole C, and bymeansaofi whichthe drill bitis lowered-through the borehol'e tow locatiori' therein" at which the diameter of the"b'oreliol'eis robe en larged. 1

ln-the' form of invention-illustrated in FIGS. I 2 .and 3i .the' upperportion of the rotary drill bit consistsof a rnandrel 1 0 having an upper pin'll threadedly'connected'to'the lower'end of thestn'ng of drill pipe B. This mand'rel' includes an-upper kelly or drill: stem member 12 slidablysplined to the main body 13 of the drill bit. The exterior l4'of thelbwefiportiori'aof! the kelly is noncircular in shape; being telescopicallyreceived' in a'companion noncircular socket'lS formedin th'e' niain bit body 13. Asanexample, the kellyexterior-l4-and:the'soclet 15 may be ofhexagonalshape to enablethe kelly l ifto be moved longitudinally with respect to thebody,-whileistill being well, or a slot in thecasing; on which 't he-cutters actzwhen the capableof transmitting rotarymotion to the'b'ody: I 3.

The body 13 has a limited range of longitudinal relative movement along the mandrel 10, its upward movement being determined by engagement of an inwardly directed body shoulder 16 with the lower end 17 of the kelly, and its downward movement being limited by engagement of a stop device 18, secured within the upper portion of the body, with a piston structure 19 serured to the mandrel. As specifically shown in the drawings, tle piston structure includes an annular piston 20 encompassing the cylindrical portion 21 of the kelly of the mandrel substantially above its hexagonal portion 14, the lower end of the piston resting upon a lower split, snap retainer ring 22 located in a peripheral groove 23 in the kelly, its upper end engaging an outwardly directed flange portion 24 of a two-piece retainer ring 25 disposed in a peripheral groove 26 in the mandrel, the piston 20 encompassing the two-piece upper retainer ring below its flange 24. Leakage of fluid between the kelly 12 and piston 20 is prevented by a suitable side seal ring 27 on the kelly engaging the inner surface of the piston 20, the piston having a suitable piston ring 28 mounted thereon slidably sealing against the inner cylindrical wall 29 of the drill bit body, which wall extends upwardly from a shoulder 30 at the upper end of the noncircular body socket 15.

The upper stop device 18 includes a stop ring 32 insertable downwardly within an upper body counterbore 32 and bearing against an upwardly directed body shoulder 33, this stop ring 31 extending across the two-piece retainer ring 25 and being held in a downward position against the body shoulder by one or shoulder by one or a plurality of split, snap retainer rings 34 overlying the stop ring and disposed in an internal groove 35 in the body.

When the body 13 is disposed in a downward position with respect to the mandrel 10, as disclosed in FIG. 1, the upper stop ring 31 may rest upon the two-piece retainer ring 25. At this time, a lower cylinder head 36, secured within the body 13 and surrounding the upper kelly or drill stem member 12, is spaced substantially below the piston structure 19. This cylinder head 36 is annular in shape, being secured to the body by a plurality of circumferentially spaced screws 37 threaded in the body and extending into a peripheral groove 38 in the cylinder head. The cylinder head has an inner seal ring 39 slidably and sealingly engaging the cylindrical periphery 21 of the kelly above its hexagonal portion 14, and also an external seal ring 40 sealing against the inner cylindrical wall 29 of the cylinder portion 41 of the main body 13 of the drill bit. 4

The body 13 has a plurality of expansible parts mounted on it. These include cutter supporting members 42 pivotally mounted in one or more body slots 43 on hinge pins 44 which are suitably secured to the body to prevent loss therefrom. Each cutter supporting member depends from the hinge pin and carries a suitable cutter 45 on its lower end. As specifically illustrated, the cutters 45 are of the toothed roller type, being designed for drilling upon relatively hard formations. However, the cutters could be constituted as drag cutters, or as milling cutters, in the event the expansible drill bit is to be employed for severing and milling away a section of well casmg.

The cutter supporting members 42 and the cutters 45 themselves tend to occupy a retracted position substantially entire ly within the confines of the slots 43 of the main body 13 of the bit. These cutter supporting members and the cutter structures are expandable outwardly to enlarge the diameter of an existing borehole, or, if milling cutters are employed, to sever and mill away a length of easing disposed in the borehole, To accomplish the expansion, each cutter supporting member 42 has an inclined expander surface 46 on its inner portion below its hinge pin 44, which tapers in a downward and inward direction, each expander surface terminating in a lock surface 47 formed on a lock portion 48 of the cutter supporting member. The outward expansion is accomplished by relatively elevating the body 13 along the mandrel 10, as described specifically hereinbelow, which will produce relative longitudinal movement between the cutter supporting members 42 and the tubular member 49 of the mandrel 10. This tubular member includes a lower portion 50 slidable within a guide bushing 51 mounted in a bridge 52 secured to the body and extending across the body slot or slots 43. The guide bushing 51 is disposed below the lock portions 48 of the cutter supporting members 42 and is secured in place by upper and lower contractible split retainer rings 53 disposed in grooves 54 in the bushing and engaging the upper and lower ends of the bridge 52.

Located initially substantially above the guide bushing 51 and below the hinge pins 44, and in cutter supporting member recesses 56, is a mandrel lock and expander 57 which has outer surfaces 58 adapted to engage the expander surfaces 46 and the lock surfaces 47 of the cutter supports 42. The lock and expander 57 may be formed integral with the tubular member 49, the upper portion 49a of the latter being piloted within a socket 49b formed in the lower portion of the kelly. This upper portion 49a is an enlarged boss engaging a downwardly facing shoulder 60 of the kelly, the tubular member being held against the shoulder by a suitable split retainer or lock ring 61 expanded into an internal groove 62 encompassing the kelly socket 49b and engaging the lower end of the tubular member boss 49a.

The apparatus includes means, generally denoted at L, for locking the mandrel 10 and the cutter supporting body 13 against relative longitudinal or telescopic movement, with the cutter supports 42 and cutters 45 in fully retracted positions, whereby when the bit assembly is being run into the borehole or into casing in an upper portion of the borehole, the cutters 45 may not be prematurely expanded. More specifically, in the illustrative embodiment, the locking means, L is constituted by a hydraulic lock provided by trapping hydraulic fluid in the annular space or chamber 65 defined between the inner cylindrical wall 29 of the body 13, the outer cylindrical section 21 of the mandrel 10, the upper piston 20, and the piston head 36 previously described.

Suitable radially extended ports 66 lead between the chamber 65 and a longitudinally extending passage 67 in the mandrel 10, which passage is also in communication with the drill string B for allowing the flow of drilling fluid in either direction. Disposed in the passage 67 is a sleeve or valve member 68 having, as seen in FIG. 1, an upper seal ring 69 engaging the wall of passage 67 above ports 66 and a lower seal ring 70 engaging the wall of passage 67 below the ports 66, so that when the sleeve 68 is in the position shown in FIG. 1, hydraulic fluid, with which chamber 65 is initially filled, is trapped in the chamber 65. The fluid in chamber 65 is thus adapted to prevent movement of the piston head 36 upwardly relative to the piston 20, and the mandrel 10 and body 13 are thereby locked against movement of the cutter supports 42 relative to the expander 57, the cutters being, accordingly, in retracted positions. A threaded filler plug opening 65c in the body leads to the chamber 65 and through which the hydraulic fluid can be placed in the chamber, this opening being closed by a threaded plug 65d.

In order to latch the sleeve 68 in a position closing the ports 66, the sleeve is provided with a number of circumferentially spaced, downwardly extended resilient latch fingers 71, each having an outwardly extended latch lug 72 thereon adapted to be disposed in an upper annular latch groove 73 in the kelly 12. The latch lugs 72 have upper radial faces 74 engageable with complemental radial faces in the groove 72 to prevent upward movement of the sleeve 68 from the position closing the ports 66. In order to permit downward movement of the sleeve 68, however, the lugs 72 have lower inclined cam surfaces 76 engageable with lower surfaces in the groove 73 for camming the latch fingers 71 inwardly when a downward force is applied to the sleeve 68.

Referring to FIG. 2, it will be seen that a downward force may be applied to the sleeve 68 by placing a ball or other plug 77 in the fluid flowing downwardly in the passage 67 of the mandrel 10, the ball landing on the sleeve 68 to prevent flow defined between the lowerf cylinder head 36 and piston'20,

therethrough, so that fluid, pressure forces the sleeve 68 downwardly, causing the latch lugs 72 tobe cammed from the grooves 73*. When the sleeve 68 moves downwardly, the ports 66- in-themandrel are opened. In order to prevent the ports fromagain being closed, the sleeve 68 is adapted to be latched 5 in" its lower position bv engagement of the latch lugs 72 in a lower latch groove 78pnr'ided in the mandrel kelly 12.

When the fluid previously trapped in the lock chamber 65 is released by opening of the-ports 66, the drill bit is in condition to be expanded by reverse circulation of drilling fluid. In this connection, the lower portion 50 of the tubular member 49 of the mandrel 10 is constituted at its lower end as a fitting 80 which is suitably connected, as by a slip fit 81, within the member 50 itself and weldedthereto, as at 82. This fitting portion 80.0f the member 49'slides in the guide bushing 51 and has a flow bean providinga small orifice or passage 83 in its lower end communicating-with a bore 84 in the fitting, this bore 84, in turn, communicating with a central passage 85 extending longitudinally through the'tubular member 49, opening at its upper end into the passage 67, inthe mandrel kelly 12. 1

Whendrilling fluid is pumped downwardly in the borehole around the exterior of the drill string B, such fluid passes around the exterior of the drill bit-A to the drilling region to flush the cuttings inwardlythroughthe slot or slots 43 of the body and toward the fitting 80 at the lower endof the tubular member, 49, the fluid thenpassing upwardly through the central orifice or passage 83 of the'flow bean and through the central, passage 85 of the tubular, member 49 into the central passage 67 through the kelly 12, fromwhere the fluid and cuttings pass upwardly thru through-the drillpipe string'B to the top of the borehole. The'fluid can also a pass through the slots 43 around the e'xterior of the mandrel 10 andinto the hexagonal portion of the body 13, leakage of this fluid upwardly around the tubular member boss 49a being prevented bya suitable seal ring 490 in the upperkelly sealingly engaging the periphery of the enlarged boss.

Assuming the body-13 of the tool to be elevated relatively along thetubular mandrellO, as seen in FIG. 3, the inclined expander surfaces 46 of the cuttersupporting members shift upwardly along the lock and expander portion 57 of the tubular member 49., During such upwardshifting, the cutter supporting members 42' and the cutters ,45 carried thereby will pivot about thehinge pins44-and, be urged in an outward direction. The upward, movement of the body 13' with respect to the mandrel can continue until the cutters ,45 have been shifted outwardlyto their fullest extend, as determined by engagement of stop shoulders 42a on the cutter supporting memberswith companion shoulders 42b formed in the body 13 on opposite sides of the bodyslot or slots 43. Whensuch expansionoccurs, the body shoulder '16 will engage the lower. end 17 of the kelly portion" of the-tubular mandrel l0, and the lock and expander 57 on the tubularmember'will be disposed behind and in engagement with the'lock portions 48 of the cutter supporting members 42:

The relative upwardmovementof thebody .13 of the tool along the tubular mandrel l0 is'accomplished by the action of fluid pressure being pumped downwardly through the annulus D surrounding,the-drilLpipe string B. This, pressure'willbe greater. than the pressure within the passages 67,185 of the tubular mandrel 10, in view of the pressure drop occasionedby the orifice 88 formed in the lowerfittingst) secured withinthe tubular member 49.1Thepressure ,within the central passage 67 will be the same pressure as exists in thecylinder. space 65 and between the periphery .21 of the kelly portion- 12.0f the mandrel and the inner wall 290i thecylindrical portion-4l of the mainbody of the drillbit, communication between the central passage67 and-the annular cylinder space 65 being provided by the opened ports I 66 in the kelly extending between the central passage 67 and the annular. cylinder space 'drill bit A- via the orifice 83, differential pressure aotihg u The cylinder head 36 itself is subject to the relatively high pressure of the fluid surrounding the bit body 13, andwhich is capable of passing upwardly through the slots 43 andaround the kelly portion 12 of the body for action in an upward direction on the cylinder head 36 over the annular area R. Thus, the cylinder head 36 is subject to the relatively highpressure of fluid acting upon it in an upward direction; whereas, the pressure of the fluid in the cylinder space 65 above the cylinder head is at a relatively low pressure, a pressure differential being provided which is capable of shifting the body 13 upwardly along the mandrel 10 until the cutters 45 have been expanded outwardlyto their fullest extend, as disclosed in FIG. 3. The fluid under pressure, as has been noted above, is developed by restricting the flow of fluid through the orifice 83' of the mandrel. As a result of such restriction of flow, the pumping of acompressed gas or drilling mud at an adequate rate downwardly throughthe'annulus D around the drill pipe and around the drill bit A-will result in a relatively high pressure of fluid being present in the well'bore' for upward action on the cylinder head 36 surrounding'the ex- I terior of the kelly 12.

In theuse of the apparatus as thus far described, the'enti're volume of drilling fluid entering. the drillstring B through the drill bit must pass through the'passage 85of the tubular man drel member 49. The orifice or passage 83in the lower fitting is sufficiently small as to cause the necessary pressure differential, whichfunctionsas indicated above to etfectexpansion of the cutters, but following such expansion, the orifice 83 is unnecessary to maintain the cutters expanded, the weight of the drillstring being imposed on the cutter supports '42, and the cutters engaging and working on a shoulder formed in theborehole and facing upwardly, as seen inFIG. 3.

Accordingly, the presentinvention also provides a structure which an enlarged flow path compared with the orifice 83for' the passage of drilling fluid and cuttings into the passageof the mandrel member 49. Thus, the tendencyof cuttings to plug the drill bit is substantially minimized.

More particularly, the fitting 80 is provided I with one or more radial ports or circulation openings 830 leading into the bore 84 of the fitting. These ports 8321 are-located along the fitting so that when the cutters are retracted (FIG. I), the ports 83 83a are disposed within the tubular guidebushing SI and are, therefore, effectively closed. Under these circumstances, drilling fluid may enter the mandrel part 49 only.

through the orifice 83 to produce the necessary differential pressure to expand the cutters 45. However, when the'cutters' are expanded (FIG. 3), the enlarged ports or circulation openings 83a are below the bushingSl, thereby p'roviding an" enlarged fluid path for thedrilling fluidand cuttings, having; much less tendency to plug than the orifice 83.

In the use of the apparatus disclosed in l, 2and'3f the cut' ters 45 are initially in their retracted'position, as-di'sclose in FIG. 1, the body 13 of the tool and the cutter-members bei I: located in their initial lower position with respectito the-ma drel 10. The drill bit A is'lowered on a string of'drilhpipe B the desired location in the'well bore at whibhthecuttersar be expanded outwardly. When such position is"reachem' -the ball 77 is placed in the drill string B and is allowed-tosettl'e' 'andi seat on the upper end'of the sleeve 68, or is *circula ted inttren gagement with the sleeve' 68 by the pumping ofia ci'rculati'rfl fluid down the drill string B andup through the annulu The application of fluid pressure down the'drill st'ringlfl lowingseating of the ball 77 on the sleeve'68, will causefthe latch fingers 71 to be cammed' inwardly by the aotion='of tlib= camming surfaces 76 on the latch lugs '72,'and 't-hetsleevei will" move downwardly to rest atthe upper end of the bbss fli i bi-" the mandrel member 49, as seenin FIG, 2.

Thereupon, when fluid is reverse circulated downtlie-an nu lus D and up the drill string B, entering the latter tlirough th wardly on the body 13 to move it upwardly will 'displace-itfiein-' itially trapped fluid-from the hydraulic lockchaniber 655 As the body '13 moves upwardly, the surface ssor niamandrer lock and expander 57 will be engaged by the inclined surfaces 46 of the cutter supports 42, causing the cutters 45 to be expanded into engagement with the wall of the hole. Rotation of the drill string B as the cutters 45 are biased outwardly will effect a cutting or milling action until the cutters are fully expanded to the positions shown in FIG. 3.

As the body 13 move. upwardly relative to the mandrel 10, the guide bushing 51 a'so moves upwardly relative to the fitting 80, so that the circulation ports 83a are ultimately uncovered, as seen in FIG. 3. After the cutters 45 are fully expanded, differential pressure across the orifice 83 is not necessary to hold the cutters expanded, the enlarged flow passages 83a then allowing maximum flow into the mandrel passage 85 with minimum tendency of clogging by cuttings removed from the borehole wall or a casing in the hole.

Referring now to 4 and 5, a modified construction is shown. In this construction, the portions of the drill bit, including the mandrel 10, the body 13, the mandrel portion 49, the kelly 12 in the polygonal bore 15, and the cutter supports 42, are all the same as in the previously described embodiment. In addition, the lower end section 50 of the tubular mandrel portion 49 is disposed in the guide bushing 51.

However, the modified construction has a fitting 180 secured at the lower end of section 50 of the tubular mandrel portion 49, which is different than the corresponding fitting 80 of the first-described embodiment. This fitting 180 has the enlarged circulation ports 183a corresponding to the ports 83a of the first-described fitting 80. At its lower end, the fitting 180 has a valve cage 280, including a downwardly facing ball J seat 380, adapted to be closed by a ball valve 480 when the bit is being run into the borehole to prevent entry of fluid into the passage in the mandrel member 49 through the fitting 180. The cage also includes a lower ball retainer ring 580 held in place by a resilient, split lock ring 680. Side openings 780 are provided in the cage for admission of borehole fluids. Under these circumstances, the drill pipe B would be run into the borehole dry, that is, without filling with borehole fluids, and the previously described hydraulic lock means L would function to prevent expansion of the bit, unless, if desired, a small bypass port 183 of reduced size is provided above the ball valve 480 and bushing 51 to allow entry of borehole fluids into the mandrel portion 49 and filling of the drill pipe string B.

In the operation of the drill bit of FIGS. 4 and 5, following release of the hydraulic lock means, reverse circulation will cause closure of the ball valve 480 against the seat 380 as fluid tends to flow into the passage 85 of the mandrel portion 49. Under these circumstances, fluid pressure outside the drill bit holding the ball valve 480 closed will force the body 13 upwardly to expand the cutters.

As the cutters are expanded during upward movement of the body 13 and the guide bushing 50 relative to the fitting 180, the circulation ports 183 will be opened, allowing admission of circulating fluid into the passage 85 of the mandrel portion 49. These large openings 183a have a minimum tendency to plug with cuttings, as do the corresponding circulation openings 83a in the first-described embodiment.

In the event that the optional port l83has been employed to run the drill string wet, this opening provides a restriction to flow, whereby to produce the differential pressure to expand the cutters of the embodiment of FIGS. 4 and 5. This restricted port 183 is closed by the guide bushing 51 when the cutters are fully expanded, as seen in FIG. 5.

The use of the check valve 480 and ports 780 prevents or restricts upward flow of well bore fluid into the mandrel l and drill pipe B during lowering of the bit in the well bore. However, large fluid volumes can still be pumped downwardly through the drill pipe B and mandrel for discharge into the well bore C, since the ball 480 will be forced downwardly against the stop ring 580 clear of the ports 780, allowing free flow of fluid therethrough. Similarly, the ball 480 will be in its lower position during elevation of the pipe B and bit A in the well bore, allowing free drainage of fluid from the pipe B through the ports 780.

lclaim:

1. In a rotary drill bit for attachment to a drill string to be rotated thereby in a borehole: a main body, laterally movable cutter means carried by said body, means for expanding said cutter means laterally of said body from a retracted position to an expanded position, and means for releasably retaining said cutter means in one of said positions comprising means providing a hydraulic fluid chamber and a passage leading from said chamber, a hydraulic fluid filling said chamber, and releasable means for closing said passage to trap said hydraulic fluid in said chamber to retain said cutter means in said one of said positions and to prevent additional fluid from entering said chamber, said closing means being movable from its passage closing position.

2. In a rotary drill bit as defined in claim I; wherein said releasable retaining means traps said hydraulic fluid in said chamber to retain said cutter means in a retracted position.

3. In a rotary drill bit as defined in claim I; said expanding man means comprising a mandrel movable longitudinally within and relative to said body.

4. In a rotary drill bit as defined in claim 1; said expanding means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means responsive to fluid under pressure in the borehole for efiecting expansion of said cutter means.

5. In a rotary drill bit as defined in claim I; said expanding means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means responsive to fluid under pressure in the borehole for effecting expansion of said cutter means, cylinder and piston means together with said body and mandrel providing said hydraulic fluid chamber.

6. In a rotary drill bit for attachment to a drill string to be thereby in a borehole: a main body, laterally movable cutter means carried by said body, means for expanding said cutter means laterally of said body from a retracted position to an expanded position, and expanded for releasably retaining said cutter means in one of said positions comprising means providing a hydraulic fluid chamber and a passage leading from said chamber, and releasable means for closing said passage to trap hydraulic fluid in said chamber to retain said means in said one of said positions, said closing means being movable from its passage closing position; wherein said releasable retaining retains said cutter means in a retracted position, said body and mandrel providing cylinder and piston means responsive to fluid under pressure in the borehole annulus surrounding the drill string for effecting expansion of said cutter means.

7. In a rotary drill bit adapted for attachment to a drill string to be rotated thereby in a borehole: a main body; laterally expansible cutter means carried by said body; means engageable with said cutter means and responsive to fluid pressure in the borehole annulus surrounding the drill string for expanding said cutter means laterally outwardly of said body; and releasable lock means for initially preventing expansion of said cutter means.

8. In a rotary drill bit as defined in claim 7; said releasable lock means including means providing a hydraulic fluid chamber and a port leading from said chamber, and valve means for initially closing said port, said valve means being shiftable to a position opening said port.

9. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, and said releasable lock means including'a chamber defined by said mandrel and a said body, one of said mandrel and said body having a port leading to said chamber, and valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relative to said body when said port is closed.

1'0. Ina rotary drill bit as defined in claim 7; said expandingmeans for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole ann.rlus"can flow upwardly and into the drill string, and said releasable lock means including a chamber defined by said mandrel and said body, one of said mandrel and said body having a port leading to said chamber,

and valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relativetosaidbody when said port is closed.

11. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providingycylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel'having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, and said releasable lock means including a chamber defined by said mandrel andsaid body, one of said mandrel and said body having a port leading to said chamber, valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relative to said body when said port is closed, and said valve means including a sleeve shiftably disposed in said passage and having means cooperable'with a plug in-a fluid streamflowing downwardly in said drill string for said port.

12. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, said releasable lock meansincluding a chamber defined by said mandrel and said-body, one of said mandrel and said body having a port'leading to said chamber, valve means for closing said port'to'confine a quantity of hydraulic fluid in said'chamber to prevent movement of said mandrel relative to said body when said port is closed, said valve means including a sleeve shiftably disposed in said passage and having means cooperable with a plug in a fluid stream flowing downwardly in said drill string foropening said port, and

means for reducing thepressure of thefluid flowing upwardly through the mandrel passage.

13. in a rotarydrill bit as defined in claim 7; said expanding means for said cutter meanscomprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder' and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through-which fluid pumped down the borehole annuluscan flow upwardly and into the drill string, said releasable lock'means-including a chamber defined by said mandrel and said body, said mandrel having a port leading to said chamber from said mandrel passage, valve means for closing said' port to confine aquantity of hydraulic fluid'in said chambertoprevent'movement of said mandrel relative to said body when said port is closed; said valve means including a sleeve shiftably disposed in's'aid mandrel passage and havingineans cooperable with a plug in a fluidstream flowing downwardly insaid drill string for opening said port, means for reducing the pressure of the fluid flowing upwardly through the mandrel passage including an orifice leading into said mandrel passage, and means providing a normally closed opening larger than said orifice opening into' said mandrel passage from the borehole'and opened'in response tolongitudirial movement of said mandrel relative to said body ineffecting expansion of said cutter means.

14. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprisinga mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in'the borehole annulus to effect expansion of said cutter means. said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, said mandrel having flow restricting means in its passage for reducing the pressure of ,the fluid flowing up.- wardly through the mandrel passage, and means for communicating the low pressure areas of said cylinder and piston means with the reduced pressure region of said mandrel passage including a chamber defined between said mandrel and said body, a port leading between said mandrel passage and said chamber, and valve means movable between a first position closing said port and a second position opening said port.

l5. ln a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, saidbody and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus .to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, said mandrel having flow restricting means in its passage for reducing the pressure of the fluid flowing upwardly through the mandrel passage, means for communicating the low pressure areas of said cylinder and piston means with the reduced pressure region of said mandrel passage including a chamber defined between said mandrel and said body, a port leading between said mandrel passage and said chamber, valve means movable between a first position clos ing said port and a second position opening said port, and means for providing a nonnally closed opening leading into said mandrel from the borehole which is opened in response to longitudinal movement of said mandrel in said body in effecting expansion of said cutter means, said enlargedtopening having a flow areaat least equal to the flow area of a said mandrel passage.

16. In a rotary drill bit adapted for attachment to a drill string to be rotated thereby in a borehole: a main body, laterally expansible cutter means carriedby said -body,:means including aninner'mandrel engageable with said cutter means and responsive to the pressure of fluid in the 'regionof the borehole externally of the drill bit .for expanding said cutter means laterally outwardly of said body, said mandrel'having a passage therethrough for the'flow of fluid from said region of the borehole upwardly into said drill string, said mandrelhaw ing means providing a circulation flow path leading from said region into said mandrel passage, said mandrelhaving a -flow restriction therein leading between said mandrel ,passageand the borehole andsmallerthansaid circulation flow pathfor reducing the pressure of fluid in saidmandrel-passage said -stringto be rotated thereby in a-borehole: aimain bo'dy,

laterally expansible cutter means carried bysaid. body -rneans including an inner mandrel engageablewithsaidcuttenmeans and responsive to'the pressure offluid in theregionrof t-he borehole externally of the drill bit for expandingvsaid cutter means laterally outwardly of said body, said mandrel havinga passage: therethrough for the flow of fluid from said region'of the borehole upwardly into said drill string, saidmandrel having means providing a circulation flow path leadinglfromsaid region into said mandrel passage and comprising anrend portionon said-mandrel, said endportion having adateral port therein defining said circulation flow pathand communicating with said mandrel passage, said end portion also having valve means for closing said mandrel passage when said circulation flow path is closed, and means closing said port until said cutter means are expanded, said port being open to provide a bypass around said valve when said cutter means are expanded.

18. In a rotary drill bit as defined in claim 17; said valve means including a downwardly facing seat circumscribing said mandrel passage, and a ball valve engageable with said seat to prevent entry of fluid from the borehole into said mandrel passage through said end portion when said circulation flow UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,554 305 Dated January 12, 1971 Archer W. Kammerer, Jr. lnventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 38, "expanded should read means line 45, after "retaining" insert means line 71 canc: "a". Column 9, line 32, after "for" insert opening Column 10, line 41, cancel "a", second occurrence. Column 11 line 5, after "valve" insert means Signed and sealed this 29th day of June 1971.

(SEAL) Attest EDWARD M FLETCHER JR WILLIAM E SCI-IUYLER Attesting Officer Commissioner of Paten1 

1. In a rotary drill bit for attachment to a drill string to be rotated thereby in a borehole: a main body, laterally movable cutter means carried by said body, means for expanding said cutter means laterally of said body from a retracted position to an expanded position, and means for releasably retaining said cutter means in one of said positions comprising means providing a hydraulic fluid chamber and a passage leading from said chamber, a hydraulic fluid filling said chamber, and releasable means for closing said passage to trap said hydraulic fluid in said chamber to retain said cutter means in saId one of said positions and to prevent additional fluid from entering said chamber, said closing means being movable from its passage closing position.
 2. In a rotary drill bit as defined in claim 1; wherein said releasable retaining means traps said hydraulic fluid in said chamber to retain said cutter means in a retracted position.
 3. In a rotary drill bit as defined in claim 1; said expanding man means comprising a mandrel movable longitudinally within and relative to said body.
 4. In a rotary drill bit as defined in claim 1; said expanding means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means responsive to fluid under pressure in the borehole for effecting expansion of said cutter means.
 5. In a rotary drill bit as defined in claim 1; said expanding means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means responsive to fluid under pressure in the borehole for effecting expansion of said cutter means, cylinder and piston means together with said body and mandrel providing said hydraulic fluid chamber.
 6. In a rotary drill bit for attachment to a drill string to be thereby in a borehole: a main body, laterally movable cutter means carried by said body, means for expanding said cutter means laterally of said body from a retracted position to an expanded position, and expanded for releasably retaining said cutter means in one of said positions comprising means providing a hydraulic fluid chamber and a passage leading from said chamber, and releasable means for closing said passage to trap hydraulic fluid in said chamber to retain said means in said one of said positions, said closing means being movable from its passage closing position; wherein said releasable retaining retains said cutter means in a retracted position, said body and mandrel providing cylinder and piston means responsive to fluid under pressure in the borehole annulus surrounding the drill string for effecting expansion of said cutter means.
 7. In a rotary drill bit adapted for attachment to a drill string to be rotated thereby in a borehole: a main body; laterally expansible cutter means carried by said body; means engageable with said cutter means and responsive to fluid pressure in the borehole annulus surrounding the drill string for expanding said cutter means laterally outwardly of said body; and releasable lock means for initially preventing expansion of said cutter means.
 8. In a rotary drill bit as defined in claim 7; said releasable lock means including means providing a hydraulic fluid chamber and a port leading from said chamber, and valve means for initially closing said port, said valve means being shiftable to a position opening said port.
 9. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, and said releasable lock means including a chamber defined by said mandrel and a said body, one of said mandrel and said body having a port leading to said chamber, and valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relative to said body when said port is closed.
 10. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill sTring, and said releasable lock means including a chamber defined by said mandrel and said body, one of said mandrel and said body having a port leading to said chamber, and valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relative to said body when said port is closed.
 11. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, and said releasable lock means including a chamber defined by said mandrel and said body, one of said mandrel and said body having a port leading to said chamber, valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relative to said body when said port is closed, and said valve means including a sleeve shiftably disposed in said passage and having means cooperable with a plug in a fluid stream flowing downwardly in said drill string for said port.
 12. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, said releasable lock means including a chamber defined by said mandrel and said body, one of said mandrel and said body having a port leading to said chamber, valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relative to said body when said port is closed, said valve means including a sleeve shiftably disposed in said passage and having means cooperable with a plug in a fluid stream flowing downwardly in said drill string for opening said port, and means for reducing the pressure of the fluid flowing upwardly through the mandrel passage.
 13. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, said releasable lock means including a chamber defined by said mandrel and said body, said mandrel having a port leading to said chamber from said mandrel passage, valve means for closing said port to confine a quantity of hydraulic fluid in said chamber to prevent movement of said mandrel relative to said body when said port is closed, said valve means including a sleeve shiftably disposed in said mandrel passage and having means cooperable with a plug in a fluid stream flowing downwardly in said drill string for opening said port, means for reducing the pressure of the fluid flowing upwardly through the mandrel passage including an orifice leading into said mandrel passage, and means providing a normally closed opening larger than said orifice opening into said mandrel passage from the borehole and opened in response to longitudinal movement of said mandrel relative to said body in effecting expansion of said cutter means.
 14. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally withIn and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, said mandrel having flow restricting means in its passage for reducing the pressure of the fluid flowing upwardly through the mandrel passage, and means for communicating the low pressure areas of said cylinder and piston means with the reduced pressure region of said mandrel passage including a chamber defined between said mandrel and said body, a port leading between said mandrel passage and said chamber, and valve means movable between a first position closing said port and a second position opening said port.
 15. In a rotary drill bit as defined in claim 7; said expanding means for said cutter means comprising a mandrel movable longitudinally within and relative to said body, said body and mandrel providing cylinder and piston means having high pressure areas subject to the fluid under pressure in the borehole annulus to effect expansion of said cutter means, said mandrel having a passage through which fluid pumped down the borehole annulus can flow upwardly and into the drill string, said mandrel having flow restricting means in its passage for reducing the pressure of the fluid flowing upwardly through the mandrel passage, means for communicating the low pressure areas of said cylinder and piston means with the reduced pressure region of said mandrel passage including a chamber defined between said mandrel and said body, a port leading between said mandrel passage and said chamber, valve means movable between a first position closing said port and a second position opening said port, and means for providing a normally closed opening leading into said mandrel from the borehole which is opened in response to longitudinal movement of said mandrel in said body in effecting expansion of said cutter means, said enlarged opening having a flow area at least equal to the flow area of a said mandrel passage.
 16. In a rotary drill bit adapted for attachment to a drill string to be rotated thereby in a borehole: a main body, laterally expansible cutter means carried by said body, means including an inner mandrel engageable with said cutter means and responsive to the pressure of fluid in the region of the borehole externally of the drill bit for expanding said cutter means laterally outwardly of said body, said mandrel having a passage therethrough for the flow of fluid from said region of the borehole upwardly into said drill string, said mandrel having means providing a circulation flow path leading from said region into said mandrel passage, said mandrel having a flow restriction therein leading between said mandrel passage and the borehole and smaller than said circulation flow path for reducing the pressure of fluid in said mandrel passage, said flow path including a portion by passing said flow restriction, means closing said portion to enable said restriction to effect pressure reduction in said mandrel passage, and said body having a surface exposed to the reduced pressure in said mandrel passage, whereby said cutter means are expanded by differential pressure externally of and acting on said body.
 17. In a rotary drill bit adapted for attachment to a drill string to be rotated thereby in a borehole: a main body, laterally expansible cutter means carried by said body, means including an inner mandrel engageable with said cutter means and responsive to the pressure of fluid in the region of the borehole externally of the drill bit for expanding said cutter means laterally outwardly of said body, said mandrel having a passage therethrough for the flow of fluid from said region of the borehole upwardly into said drill string, said mandrel having means providing a circulation flow path leading from said region into said mandrel pAssage and comprising an end portion on said mandrel, said end portion having a lateral port therein defining said circulation flow path and communicating with said mandrel passage, said end portion also having valve means for closing said mandrel passage when said circulation flow path is closed, and means closing said port until said cutter means are expanded, said port being open to provide a bypass around said valve when said cutter means are expanded.
 18. In a rotary drill bit as defined in claim 17; said valve means including a downwardly facing seat circumscribing said mandrel passage, and a ball valve engageable with said seat to prevent entry of fluid from the borehole into said mandrel passage through said end portion when said circulation flow path is closed.
 19. In a rotary drill bit as defined in claim 17; said valve means including a downwardly facing seat circumscribing said mandrel passage, and a ball valve engageable with said seat to prevent entry of fluid from the borehole into said mandrel passage through said end portion when said circulation flow path is closed, and said mandrel having a restricted opening leading into said mandrel passage above said end portion for enabling restricted entry of fluid from said borehole into said mandrel passage when said circulation flow path is closed. 